Drug & supplement interaction

Lavender + Fosphenytoin Sodium

Fosphenytoin Sodium brand name: Sesquient.

Moderate Interaction
Medically reviewed by · Updated September 2026
The bottom line Moderate

Lavender has a moderate interaction with Fosphenytoin Sodium. Theoretically, lavender might potentiate the therapeutic effects and adverse effects of CNS depressants.

Read the full interaction report
SeverityModerate
LikelihoodUnlikely
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Lavender and Fosphenytoin Sodium

Here is the interaction we found between these two, with the evidence behind it.

Moderate

CNS DEPRESSANTS

Why this applies to Fosphenytoin Sodium

Fosphenytoin Sodium falls under CNS DEPRESSANTS — the group Lavender interacts with.

Theoretically, lavender might potentiate the therapeutic effects and adverse effects of CNS depressants.
Laboratory research suggests that lavender has sedative effects. However, clinical studies in patients taking oral lavender oil (Silexan) 160 mg for 10 weeks or taking lavender flower powder 1 gram daily for 2 months have not reported side effects of drowsiness, sedation, or sleepiness. There is still some concern that higher doses or different preparations of lavender might have additive effects with CNS depressant medications.
Severity Moderate Likelihood Unlikely Evidence D

Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans..

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Fosphenytoin (Sesquient) is a seizure medicine that your body converts into phenytoin. Like many anti-seizure drugs, it can make you feel drowsy, dizzy, or unsteady on its own. The concern here is simply that lavender may have mild calming, sedative effects of its own, so pairing the two could add up to more sleepiness or grogginess than either one alone.

I want to be honest that this is a theoretical caution based on how these things behave, not on real-world reports. In fact, human studies of oral lavender (like Silexan 160 mg) didn't show much sedation. Stronger or larger doses might matter more. This won't change how well your fosphenytoin controls seizures. Still, if you notice extra drowsiness, check in with your pharmacist or doctor before changing anything.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Schulz V, Hansel R, Tyler VE. Rational Phytotherapy: A Physician's Guide to Herbal Medicine. Terry C. Telger, transl. 3rd ed. Berlin, GER: Springer, 1998.
  2. Farshbaf-Khalili A, Kamalifard M, Namadian M. Comparison of the effect of lavender and bitter orange on anxiety in postmenopausal women: A triple-blind, randomized, controlled clinical trial. Complement Ther Clin Pract 2018;31:132-8. PubMed
  3. Donelli D, Antonelli M, Bellinazzi C, Gensini GF, Firenzuoli F. Effects of lavender on anxiety: A systematic review and meta-analysis. Phytomedicine. 2019;65:153099. PubMed

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Lavender Also Interacts With Other Medications

Lavender has 247 moderate known drug interactions in our database — the Fosphenytoin Sodium one above is one of them. If you take anything else, check it against the full list below.

Moderate 247 No known interaction 2,583 (incl. Fosphenytoin Sodium)
Taking anything else?

Check Another of Your Medications Against Lavender

Covers the 2,830 medications we’ve checked against Lavender. Pick one to open its full report.

From our Q&A

Questions About Lavender or Fosphenytoin Sodium

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Lavender or Fosphenytoin Sodium, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Fosphenytoin Sodium

This page covers Lavender only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Fosphenytoin Sodium page lists 212 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: 1,4-butanediol (major), American Hellebore (major), Arsenic (major), Beer (major) and Cesium (major).

By severity: 14 major · 179 moderate · 19 minor.

From our pharmacist’s overview on the Fosphenytoin Sodium page

“Fosphenytoin sodium (Sesquient) converts to phenytoin in the body, and phenytoin is unforgiving about blood levels. A little too low invites seizures, a little too high brings toxicity.”

Reviewed by 2 · Jul 18, 2026

Open the Fosphenytoin Sodium interaction page

One more smart check

Taking Lavender as Part of a Dietary Supplement Product? Check It for Interactions

We hold 75 real supplement products containing Lavender, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Lavender. Your product may carry other ingredients that interact with Fosphenytoin Sodium too, on top of Lavender — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Lavender and Fosphenytoin Sodium Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Lavender
Top 25%

#319 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Fosphenytoin Sodium
Top 25%

#431 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Lavender

What is Lavender?

Lavender
  • Anxiety and stress
  • Sleep problems
  • Relaxation and calming
  • Minor skin conditions
  • Aromatherapy

Lavender is a fragrant herb most popular for promoting relaxation, easing anxiety, and supporting sleep, with some encouraging evidence for a standardized oral lavender oil product for anxiety. While generally well tolerated, the essential oil should never be swallowed unless made for that purpose, and pregnant or breastfeeding people should use caution and talk to a healthcare provider first.

Read the full Lavender monograph & all interactions
Keep checking

Other Drugs & Lavender

Browse every other medication we’ve checked against Lavender — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
247Moderate
0Minor
2,582No known interaction
247 Moderate 2,582 No interaction
Moderate

247 interactions

Showing 60 of 247 moderate interactions — see all 247 on the Lavender page.

No interaction 2,582 drugs checked — show the list

We also checked Lavender against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,582 medications checked with no known interaction — see the full Lavender list.

See the full Lavender interactions page
See every supplement checked against Fosphenytoin Sodium, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Lavender monograph › Uses, safety, and every drug interaction in one place Fosphenytoin Sodium supplement interactions › Every supplement checked against Fosphenytoin Sodium, ranked by severity Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Lavender and Fosphenytoin Sodium Together: Common Questions

Can you take Lavender with Fosphenytoin Sodium?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Lavender and Fosphenytoin Sodium interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Still Have a Question About Fosphenytoin Sodium and Lavender?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.